Question

Emitter bias requires _______

(a) only a positive supply voltage

(b) only a negative supply voltage

(c) no supply voltage

(d) both positive and negative supply voltage

I got this question during an interview.

Asked question is from Input Bias and Offset Currents of the Bipolar Differential Amplifier in division Differential and Multistage Amplifiers of Electronic Devices & Circuits

Answer 1

Right option is (d) both positive and negative supply voltage

To explain I would say: If a dual power supply is there, then it is the most useful, and provides zero bias voltage at the emitter or collector for load. The negative supply is used to forward-bias the emitter junction through emitter resistor. The positive supply is used to reverse-bias the collector junction. Also has good stability.